Traditional imagesetters used in the pre-press area of a printing operation use vacuum to hold films to a rotating drum while exposing them using a laser. In order to image directly on lithographic printing plates both in Computer-to-Plate and Computer-to-Press systems, a method of holding metal plates to the outside surface of a rotating drum, or cylinder, is desired. Due to the higher stiffness and thickness of metal printing plate the force of the vacuum, limited to atmospheric pressure, is insufficient to reliably hold a metal plate onto a drum, in particular a rotating drum. Prior art solutions involve clamps (both mechanical and magnetic) as well as using steel plates on magnetic drums. Since most lithographic printing plates are made of aluminum and are non-magnetic it is desired to have a system holding the plate without clamps and without relying on magnetic properties. The plate can be imaged on the drum (as done in Computer-to-Plate and Computer-to-Press) or pre-imaged and mounted later on the plate cylinder of a printing press. In the latter applications using vacuum instead of clamps allows nearly gapless plate mounting and simplified automatic loading of plates. The invention can also be used to load thin metal backed flexographic plates onto a press and other metal backed plates. The invention is also useful when clamps are used, as it reduces the force required to hold the plate. Any combination of clamps and vacuum is improved by the invention.